Electric iron with thermokinetic switch



May 17, 1949. A. s. THOMAS ELECTRIC IRON WITH THERMOKINETIC SWITCH 2 Sheets-Sheet 1 Filed Aug. 14, 1943 INVENTOR May 17, 1949.

A. G. THOMAS ELECTRIC IRON WITH THERMOKINETIC Filed Aug 14, 19 43 SWITCH 2 SheetsSheet 2 55 90 6 -70 7 5 as 52 6 72 84 55 62 as 56 65 66 M (M 74 87 57 ,l 66 I 67 i 59 I a I I "I1 1 Iii/171i 0 7 a/ a0 INVENTOR Patented May 17, 1949 ELECTRIC IRON WITH THERMOKINETIC swrrcn Albert G. Thomas, Lynchburg, Va. Application August 14, 1943, Serial No. 498,621 8 Claims. (01. 219-25) This invention relates to electric irons and other devices and is acontinuation-in-part of my co-pending application, Serial No. 446,685,

filed June 12, 1942 issued August 14, 1945 as Patent No. 2,382,587.

An object is to provide an electric iron that will maintain the current connection to its heating element as long as the iron is kept in movement, from use, but which will break the current connection if the iron is left stationary for a period longer than a predetermined interval. In this way fires can be prevented and scorched or burned ironing boards will be obviated.

Another object is to provide an iron with an automatic current cut-off, depending upon movement of the iron and also with a thermostatic current cut-off.

A further object is to provide an iron with an automatic cut-off, depending upon movement of the iron, and also with a thermostatic cut-oil, the latter dominating the former so that movement of the iron will not close the circuit of the heating element if the iron is hotter than a predetermined temperature as determined by the setting of thermostat.

An additional object is the provision of the roller weight attached to'the arm of a switch for above features in combination with an adjust- I able thermostat.

Another object is to provide an iron with the above described characteristics, of simple and practical construction, so that it will stand up under long usage and yet will be cheap to manufacture.

A further object is the provision of an electric iron that will lift its sole plate above an ironing board or other supporting surface, after an interval, if it is left stationary and in ironing position.

Another object is-to provide an electric iron that will lift itself above its supporting surface after being left stationary for an intervaLand which will also cut off the current to the heating unit.

A still further object is the provision of an electric iron that will lift its heating unit above its ironing surface, if left stationary for an interval.

An additional object is to provide an attachment for electric irons, which will automatically cut oil the current to the heating element if the iron is left stationary for an excessive interval.

Other objects will appear in the specification.

In the drawings:

Figure 1 is a top plan view of the inner base or weight of an electric iron, showing automatic cut-oil mechanism for the heating element switch.

Figure 2 is a. view similar to that of Figure 1, but showing an alternative construction.

Figure 3 is a side elevation, in part section, of an electric iron which lifts its bottom surface above an ironing board or other support, after being left stationary for a predetermined time a connection plug for an electric iron, the plug having a, switch which automatically cuts oil the current to the iron, if left stationary for an excessive interval as determined by a thermostat or other timing device.

Figure 6 is an end view of an inertia operated of an automatic switch cut-oil for an electric iron, adapted to be connected into the cord circuit. This switch is escapement-controlled so that its operation is independent of the temperature of the iron.

In Figure l, integral arms i and 2 are pivoted to swing horizontally above weight or plate 8 of the iron which contains the heating element 4, shown in fragmentary manner. Pivot pin I is passed through a suitable bore at the junction of arms I and 2 and is threaded into a hole in weight 3, or otherwise fastened. One end of tension spring 6 is fastened to arm i by means of a hole or pin 1 and the other end is similarly fastened to weight 3 or to another support at point 8. Flexible metal strip 9 with attached electrical contact In is riveted or otherwise fastened to arm I, with mica or other suitable insulation i l intervening. One end of wire I! is flexibly connected to strip 9 and the other end leads to terminal post l3 suitably insulated from weight 3 by mica or otherwise. Electrical contact i4, mounted on bracket l5 which is fastened to weight 3 by means of screw I6 or in any suitable manner, is insulated from the weight and is connected with insulated conductor ll leading to insulated connection post l8 to which is connected one end of heating wire or element 4 which also is insulated from the'metal of the iron.

Conductor or wire I! i shown as being placed above it. The other end of heating wire 4 is connected to insulated terminal post I9 supported on weight 3. Current may be supplied to the heating element 4 by a connection plug having current connections making contact with elements l3 and I9.

Recess or trough 20 is provided in weight 3 so that ball 2|, preferably rather heavy, can roll lengthwise therein. This ball is of such size that it will strike arm 2 as it rolls in rearward direction. While recess 20 is shown it is obvious that it is not essential as ball 2| may be guided to roll on the surface of weight 3 by means of a raised U shaped or rectangular boundary strip fastened to the weight. Flexible spring strips 22 are fastened to the weight at either end of the trough 20 to act as flexible buffers for the ball, to reduce noise.

Bimetal strip 23 is fastened at one end to block 24, integral with or fastened to weight 3, by means of screw 25. Cam 26, fastened to rod 21 having rotary bearing in a suitable bore or hole in weight 3, serves as a stop for bimetal strip 23 which is urged in rearward direction by its own resiliency. Rod 21 is extended vertically and passes through a hole in the cover, not shown, of the iron so that the cam may be rotated to place strip 23 nearer to or further from arm 2 as desired. A suitable indexed knob may be fastened to the upper end of rod 21 and this knob may be rotated relative to a temperature or other scale placed on the outside of the cover. Friction means may be provided to hold rod 21 in any set position. The proximity of strip 23 to arm 2 for any given strip, de ermines the temperature at which the switch will be opened.

Threaded holes 28 may be provided in weight 3 so that the cover and handle may be attached by means of bolts or screws. Stop 29 against which switch arm I is pulled by spring 5, when the switch is in open position, is fastened to weight 3 or is integral therewith.

Fastening point 8 is so positioned that spring 3 will lie to one side of pivot when arm I rests against stop .29 and lies on the other side of pivot 5 when arm I is moved toward contact I4 sufiiciently. When this happens contact II! touches contact I4 so that current is supplied to heatingelement I.

In operation, if the switch is in open circuit position as shown and if the iron is cold so that bimetal strip 23 is in the position indicated the switch may be closed by standing the iron on its rear-end so that the weight of ball 2| will force arm 2 down to bring arm I toward contact It so that spring 6 will pass over pivot 5 and contact Ill will'be pressed against contact I4. Or, the iron may be moved forward and backward rapidly for a few strokes so that ball 2! will roll against arm 2 and will move it rearward to cause the snap action of the switch to close the circuit- When this happens arm 2 will be carried nearer to strip 23.

When the iron reaches a predetermined temperature, dependent upon the setting of cam 26, bimetal strip 23 will have bent to the left sufliciently to strike arm 2. When this happens the heating circuit will not be immediately broken, on account of the flexibility of strip 8, but current will continue to energize heating element 5 until arm I has been moved toward stop 29 a suiflcient distance for spring s to cross over pivot 5 and s to snap arm I against stop 29. Contact I6 is then separated from contact It and the heating\ ircuit is broken. This arrangement is 2 provided. so that the iron will not cool down sufliciently to withdraw thebimetal from arm 2 before the switch is snapped open. If thermostatic element 23 is a snapping disc or similar type giving quick appreciable movement in one direction or the other, then flexible strip 9 would not be neededand contact I!) can be fastened to an insulated support on arm i.

When the switch is opened by the thermostat it will remain open as long as the iron remains stationary. The iron will then cool and strip 23 will return to the starting position shown. If, however, the iron is given normal movement of use, ball 2! will be caused to roll back and forth in trough 20 so that the ball will strike arm 2 and will knock it rearward, with the result that arm I will be carried toward contact it and spring 6 will snap over pivot 5 to bring contact in against contact M to close the heating circuit.

Bimetal strip 23 is preferably of such strength or rigidity that it will prevent closing of the switch,'due to action of the ball, unless the temperature of the iron is below the value as determined by the position of cam 25. This can be true even if the iron is turned up .on end.

While tension spring 6 is shown, it is obvious that a form of compression spring or a flat spring pressing against plane surfaces on the junction of arms I and 2, can be used. The cover or any other suitable guard can prevent ball 2i from falling out of trough 23 if the iron is turned on end.

If the user leaves this iron in ironing position for a period longer than a safe interval, then the switch will be automatically opened, to prevent fires or burned boards or the like. If, however, the iron is kept in forward and backward movement, as in normal use, then the action of ball 2| on arm 2 will keep the switch closed, as long as the temperature of the iron is below that set by the thermostat.

In Figure 2, iron weight 30 contains heating element 3i one end of which is connected to insulated contact 32 and the other end of which isconnected to insulated terminal 33. Wire 34 connects the other terminal 35 with metal arm 36 through a flexible connection. This arm carries contact 31 and is pivoted to block 38 by pin or screw 39. Block 38 and stop 46 are fastened to and are insulated from weight 30. Tension spring 4| is fastened to sector 52 at point 43 and the other end of the spring is fastened to weight 30 at point 46. Spring 4! may be insulated from weight 30 or sector 42 may be of insulating material such as a heat resistant ceramic. Lugs 45 and 4t depend from sector 42 and are adapted to strike arm 36 at the end of travel of sector 42 in either direction.

Weight 41, which may be fixed to the end of arm 36 or pivoted to it with a lost motion connection as shown, serves to force arm 36 forward during useof the iron, due to momentum of the weight, so that spring M will snap over to the left of pivot 39 and lug 45 will press arm 36 to the left to force contact 31 against contact 32 to close the heating circuit. If the temperature becomes excessive, bimetal strip is fastened to support 43, willbend and will force sector 42 to the right until spring 4i passes to the right of pivot 39 so that sector 62 will be snapped to the right until lug 46 strikes arm 36 and forces it against stop 38 thereby breaking the heating circuit.

The lost motion connection of sector :32 with arm 35 allows the heating circuit to remain closed until the spring is moved over open it, although the momentum .the pivot point of arm 88 and sector 42. Support 48 may be rotatable so that position of strip 48 relative to sector 42 may be adjusted. The contact 82 may be placed at a greater arcuate distance from a perpendicular cross line through pivot than stop 48, so that once the switch is closed, the momentum of weight 41 will not be sufllcient to in the opposite direction will be enough to close it. Holes 58 for attaching the cover and handle may be pro- Vided as in Figure 1.

In Figure 3 the iron has handle 5| attached to cover 52 which has slot 58 for lever arm 54 and slots 85 and 58 for legs 51 and 58 respectively. Leg 8'! is pivoted to the cover or to the sole plate 88 by pivot 58 and leg 58 is similarly pivoted by pivot 8|. Link arm 82 is pivoted to a branch of leg 51 at 88 and to lever arm 54 by pivot 84. Ann 84 is pivoted to support 85 by pivot 88. Support 85 is-fastened to plate 81 containing a suitable electrical heating element and has offset extension 88 to which catch 88 is pivoted at 18. Spring II normally urges catch 88 in downward direction against a suitable stop. Bent arm I2 is integral with catch 88 and is positioned to be struck by weight 13 fastened to arm 14 which is attached to shaft I5 having bearing in escapement controlled or other time switch I8 fastened to plate 81 orto any suitable part of the iron. This time switch may be similar to that shown and described in my above mentioned co-pending application. Spring 11, attached to support 88 and to arm 14 tends to pull this arm to the left, the rate of movement being controlled by an escapement or other delaying means.

Link arm I8 is pivoted to arm 54 at T8 and to arm 88, integral with leg 58, at 8I. Notched arm or hook 82 is integral with arm 54 and is normally held in the position shown by catch 88.

' Connection plug 88 is fastened to the iron, and wire 84, properly insulated, makes connection with a switch contact in switch 18, through thermostat 85. The other switch contact is connected to wire 88 leading to the heating element. Likewise, wire 81 leads from plug 88 to the other terminal of the heating element. Tension spring 88 is connected between arm 54 and plate 81 or other part which may be of any desired thickness or weight. This plate is screwed to or otherwise fastened to sole plate 88, or it can be held by pressure. Spring 88 could of course be attached to cover 52 or some other part.

In operation, as long as the iron is used, the movement keeps weight I3 thrown back out of contact with arm 12, a ratchet being provided to allow free movement of weight I8 in the rearward direction, against the tension of spring H, but causing the weight to be delayed in forward direction by means of an escapement or other time delay means. Therefore as long as the iron is used the le s 51 and 58 remain folded within the iron casing as shown.

If, however, the iron is left stationary for a period longer than a predetermined interval, determined by the tension of spring I! and the escapement, weight 13 will be pulled forward in a circular path by spring I1 and will strike arm I2 which lifts catch 88 and releases lever arm 54 which is quickly pulled to the left by spring 88. When this happens, legs 51 and 58, through linkages 82 and I8, are rotated outward about pivots 58 and 5| and are brought down to positions below sole plate 88. This immediately lifts sole plate 88 above the cloth or other supporting sur- I8 and throws it back to the rear. Then catch It would be preferable 88 will engage book '82 and legs 81 and 88 will have been pulled back into the iron, around pivots 58 and 8|, by linkages 82 and I8.

Legs 51 and 58 may be of any desired shape and may be placed in any desired locations. They may be arranged to slide out of the iron along linear paths if desired. Thermostat '88 can be used to prevent the iron from overheating in use;

This iron therefore both cuts off the current and lifts the hot sole plate above the supporting surface, if it is left stationary too long in ironing position. The time switch, however, keeps the heating circuit closed for brief periods of rest so that the contacts will not be constantly arcing.

In Figure 4 handle 8| is attached to iron cover 82 to which are fastened bottom lugs or plates 88, by means of screws preferably. Relatively heavy metal plate 84, containing a suitable heating element which may be detachable, is provided with shoulders which strike plates 88 when compression springs 88, fastened to or guided by cover 82 in any suitable way, push against flanges 81 to lift cover 82 and plate 84. These flanges are integral with'rods 88 which are slidable in guide openings in plate 84. Springs 88 surround the upper ends of rods 88 as shown. Sole plate 88 is-fastened to the lower ends of rods 88. This plate is preferably made rather thin so that it will cool quickly when separated from plate 84.

Plate 84 may be rather solid with an imbedded heating unit or it can be made of two or more plates bolted or screwed together, with a heating unit between. Likewise, the heating wires could be placed in grooves in the bottom of plate 84 which could be of fire resistant ceramic material. to have mica between the heating wire and the sole plate.

Time delay switch I88, shown diagrammatically, may be of the same general type as disclosed in my co-pending application, Serial No. 446,685, filed June 12, 1942. This switch has weight I8I fastened to the lower end of arm I82 which is fastened to shaft I 83 having bearing in the switch or casing. As shown in the prior application, although in reverse direction, weight I8I will be moved against the tension of spring I84 which is fastened to arm I82 and to the switch casing, when the iron is accelerated forward and when the iron is stationary or is accelerated in reverse direction weight I8| will act against a retarding escapement so that spring I84 will pull arm I82 slowly in clockwise directionto close a pair of contacts to which wires I81 and I88 lead. Wire I88 leads also to a terminal of the heating element in plate 84, through thermostat I 88 and wire I8! is connected with terminal plug II8 fastened to the iron. Wire I I I connects the other terminal of the heating element with the remaining terminal of plug II8.

Latch II2, pivoted to the casing of switch I88 at H8 is normally held down against stop II4 on the casing of the switch by means of compression spring 5 connected between lower arm springs 96 quickly lift IIB of the latch and a support point on switch Theinset surfaces of the ends of plate 94 are vertically slidable relative to plates 93 so that when .handie 9| is pressed down to compress springs 99 and to slide plate 94 downward relative to rods 98, a. left flange 91 lifts latch I I2 which is then pressed up against the flange by springs 96 acting against cover 92. The sliding movement of plate 94 insures that sole plate 99 will be pulled up tightly against heating plate 94 since springs I n press plate 94 downward but allow latch m to pass under flange 91 and thus to hold sole plate 99 yieldingly in contact with heating plate 94. When the handle is released the springs I I1 force heating plate 94 tightly against sole plate 99. The heat conduction will then be good and the iron can be used.

Latch II2 has an inclined surface so that it will be moved to the right when flange 9 1 strikes it from underneath.

In operation, if the iron gets too hot, thermoleft stationary and in ironing position longer than a certain time interval, weight I9I will be pulled in clockwise direction, against the controlling escapement or other device, and will strike arm IIB. when this happens latch H2 is moved to the right, away. from flange 91, and

cover 92, plate 94 and attached parts upward until the top surface of plate 94 strikes the under surfaces of flanges 91, as illustrated. In this position sole plate 99 is separated from heating plate 94 and the thin sole plate will quickly cool. Rods 98 can be of poor heat conductivity metal such as some grades of steel or they can be of nonmetallic material.

Switch I99 cuts off the current in wires I91 and I99 whenweight I9I strikes arm H6, in sirnilar manner to that described in the above mentioned application.

As long as the iron is kept in movement weight I9I is kept thrown away from arm I I6 so that sole plate 99 is held against heating plate 94 but if for any reason the iron is forgotten or neglected for a period longer than an interval which may be settable, the hot iron is lifted above the sole plate to prevent burning and at the same timeY the heating circuit is opened.

Latch H2 or a similar latch can also be arranged to be pressed against flange 91 at the rear, to prevent binding.

Sole plate 99 can be pivoted tolinkages which may be pivoted to the sides or in grooves in plate 94 so that a swinging or rotary movement will lift the iron above the sole plate. Many other changes of detail can be readily made.

In Figure the casing II 8 of the iron connection plug shown is preferably made of heat resistant electrical insulating material. Weight H9 is fastened to arm I29 which is pivoted to the casing at I2I. Tension spring I22 is fastened to arm I29 and to some part of the plug such as metallic connector I23 adapted to make electrical connection with a terminal of an electric iron. A similar connector is placed on the cut-away side of the plug for connection with the other heating unit terminal of the iron.

Conductor I24 of the iron connection cord is brought into the plug through opening I25 and is electrically connected to the connector not shown. The other cord conductor I29fis connected to switch contact I21 fastened to the casing. Metallic arm I29 is provided with switch contact I28 which closesthe heating circuit by touching constat I99 will breaktlle circuit and if the iron is Spring I22 tact I21 when weight "9 is thrown to the left to past pivot I2 I.

In the open circuit position shown, arm I29 rests against stop I29 projecting from the casing. This stop is preferably of such length that am I29 is positioned just slightly past so that excessive momentum will not be required to throw weight I I9 forward to close the heating circuit. Contact I21, however, is positioned so that spring I22 will be well to the left of pivot I2I so that the rearward movement and stopping of weight H9, during ironing, will not open the switch. If, however, the iron overheats, beyond a predeterminedtemperature rise, the heat will be transmitted to thermostatic bimetal strip I39 fastened to casing IIB by a screw or otherwise, so that it will bend to the right and will force arm I29 to the pmtion shown, resting against stop I29, with the heating circuit open. The circuit will remain open unless the iron is given normal movement as in use, in which case weight II9 will be thrown to the left by the momentum, to close the heating circuit through contacts I21 and I29 and spring I22 if the iron has in the meantime cooled sufficiently to allow strip I29 to bend back to the left a sumcient distance.

The section I3I of the casing may be made of metal and may be so designed that it will come into contact with a hot surface of the iron, .to facilitate transfer of heat to the bimetal I39.

This connection plug can be adapted for use with many different types of electric irons and will provide an automatic cut-ofi feature for the heating element, if the iron is not used. This device can be placed in the cord circuit at any position where it will be given movement but if separated from the iron a timing switch such as switch I99 of Figure 4. should be used since this switch is not dependent upon the temperature of the iron for operation. e

In Figure 6, roller I92 is a metal cylinder fastened to the end of switch arm I33 by means of screw I34 which passes through a central hole in the roller and is threaded into the end of arm I33. This roller is supported by track I35 which may be any suitable surface of the iron. By this construction roller I32 may be quite heavy, in order to furnish considerable momentum to close the switch when the iron is used, but its weight will be supported and it will not tend to bend the switch arm or produce excessive friction.

In Figure '1 switch casing I39 is preferably of non-conducting plastic material or of porcelain or the like. It may be split and the parts joined by bolts. Switch arm I31 carrying ratchetpawl I38, is pivoted to the casing by pivot I39 and coiled spring I 39, attached to arm I31 and to the casing, urges the arm in clockwise direction. Gear I41 having bearing on stub'shaft I42 one end of which is screwed or otherwise fastened to casing I36, is placed adjacent a side wall of the casing and is provided with suitable indentations I43 which may be engaged by ratchet I38 to rotate gear I in clockwise direction. Ratchet I98 allows free movement of arm I31 in counter clockwise direction against the torsion of spring I49. Gear I is meshed with pinion I44 rotatable around a suitable stub shaft al ng with attached star wheel I45 which eng ,ges pivoted escapement or verge I48 which limits the rate of movement of arm I31 in clockwise direction.

Flexible metal switch contact I41 is fastened to casing I39 and is connected to one of the conductors in iron cord I48. The other conductor is connected to conductor I49 which isconnected the" vertical,

to a conductor in iron cord IE at the opposite end of casing [38. The other conductor of cord I50 is connected to metal arm I37 through conductor. III which may be' suitably insulated if desired.

' Metal ball I! is adapted to roll on an inner surface 01' the switch and if the-iron cord is given normal movement this ball will oscillate and will strike arm I31 with the result that this arm will be pushed into contact with flexible strip I41 with a certain amount of overlap. When this happens the circuit supplying energy to the heating element of the iron will be closed through conductor i5l, spring 0, arm I31 and strip I".

As long as the iron is kept in use the rolling action of ball I52 will keep arm I31 in contact with strip I47 but if the iron is left stationary for an interval greater than a predetermined amount, depending upon the overlap, the tension in spring I40, and the escapement, then arm I31 will be slowly rotated in clockwise direction until it is out of contact with strip I" and the circuit will be broken.

It is obvious that many detailed changes can be made. For instance, ball I52 could be attached to arm I31 or it could be designed to be effective when moved in any direction, by means of universal connections.

What I claim is:

1. An electric iron comprising, an ironing element, a heating element therefor, a handle, a switch for opening and closing a circuit including said heating element, snap-acting springoperated means for holding said switch closed or,

open, an iron-motionw-responsive weight for moving the snap-acting means to close said switch, and time-delay means for moving the snap-acting means to open said switch.

2. An electric iron comprising, an ironing element, a heating element therefor, a handle, a switch for opening and closing a circuit including said heating element, snap-acting springoperated means for holding said switch closed or open, a rollable element responsive to movement of said iron for moving the snap-acting means to close said switch, and time-delay means for moving the snap-acting means to open said switch.

3. An electric iron comprising, an ironing element, a heating element therefor, a handle, a switch for opening and closing a circuit including said heating element, snap-acting springoperated means for holding said switch closed or open, a ball responsive to ironing movement of said iron for movingthe snap-acting means to close said switch, and time-delay means for moving the snap-acting means to open said switch.

4. An electric iron comprising, an ironing element, a heating element therefor, a handle, a switch for opening and closing a circuit including said heating element,snap-acting springoperated means for holding said switch closed or open, a ball ve to ironing movement of said iron for moving the snap-acting means to close said switch, means for guiding movement of said ball, and time-delay means for moving the snap-acting means to open said switch.

5. An electric iron comprising, an ironing element, a heating element therefor, a handle, a switch for opening and closing a circuit including said heating element, snap-acting springoperated means for holding said switch closed or open, an iron-motion-responsive weight for moving the snap-acting means to close said switch, time-delay means for moving the snap-acting means to open said switch, and means for adjusting said time delay means for various delay periods.

6. An electric iron comprising, an ironing element, a heating element therefor, a handle, a

. switch including a resilient contact member for opening and closing a circuit including said heating element, snap-acting spring-operated means for holding said switch closed or open, an ironmotion-responsive weight for moving the snapacting means to close said switch, and time-delay means for moving the snap-acting means to open said switch.

'7. An electric iron comprising, an ironing element, a heating element therefor, a. handle, a switch including a pivoted arm for opening and closing a circuit including said heating element, snap-acting means including a pivoted member and a spring for holding said arm in closed-switch or open-switch position, said pivoted member including a pair of separated elements for striking said arm on opposite sides thereof, an ironmotion-responsive weightior moving said arm to close said switch and to cause said pivoted member to maintain said switch closed, and time delay means for moving said pivoted member to move said arm to open-switch position and to maintain said switch open.

8. In an electric iron, a. heating element, a switch for opening and closing a circuit including said heating element, snap-acting springoperated means for holding said switch closed or open, an iron-motion-responsive weight for moving the snap-acting means to close said switch, and time-delay means for moving the snap-acting means to open said switch.

ALBERT G. THOMAS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,366,480 Balda Jan. 25, 1921 1,422,224 Poole July 11, 1922 1,607,551 Mailey Nov. 16, 1926 1,659,636 Null Feb. 21,1928 2,143,701 Kelly Jan. 10, 1939 2,219,506 Steimel et al. Oct. 29, 1940 2,382,587 Thomas Aug. 14. 1945 

